So maybe the girl's arc looks like this: she starts out from a constricted life in which she has to be careful, fearful, and controlled--which naturally makes her resentful and perhaps a bit snappish (here comes the unlikeable character again, sigh). The events of the story must move her forward, point by point, to where by the end she is stepping into her own power; she's on the verge of exploring her abilities, limits, etc.

I think when the story starts, she lives a life under the control of others. During the course of story, she's...hmm...she's under a different kind of control until about a third of the way through. Then she's on her own, and must make her own choices, do her own thinking for the first time. So what about the last 2/3 of the story? What's her arc about then?

Must think some more.